Audio and video magnetic tape cassettes typically include two reels mounted within a housing with a length of magnetic tape wound around the two reels and extending between the reels across an access opening. Slack or looseness in the tape between the reels can arise when the cassette is transported or is separated from its associated recording and/or reproducing device, commonly called a recorder. While some cassettes have locks which restrict rotation of the reels when the cassette is not in the recorder, it is still possible for one or both of the reels within the cassette housing to turn to unwind the tape and develop slack in the portion of the tape extending between the reels. Slack in the tape can also occur when the tape is engaged with the recorder if driving and braking the reels during the operation of the recorder is not performed synchronously and at the same rate. This slack may cause the tape to jam within the cassette housing or within the recorder and can lead to defective recording or playing operations.
Slack limiters for avoiding slack in the tape are described in numerous patents. U.S. Pat. No. 4,813,628 to Tollefson discloses a tubular slack limiter. U.S. Pat. Nos. 4,773,615 to Carroll, 4,639,967 to Bordignon, 4,598,329 to Nelson, 4,569,492 to Gelardi et al., 4,518,135 to Gebeke, 4,405,097 to Gebeke, and 4,382,565 to Shiba all disclose slack limiters having a generally common configuration. These slack limiters include a resilient, flexible strip which is generally made of a plastic material. The strip is fixed at one end to the cassette housing and has a free end which can be coated with a layer of low friction material such as polytetrafluoroethylene and which contacts the tape.
All of these slack limiters operate by pressing the tape against a stationary portion of the cassette housing, such as a guide pin, and frictionally preventing the tape from unwinding from the reel and developing slack. These slack limiters are also known as wiper tabs and contact and provide a force on the tape. However, this contact scratches and wears the tape surface and can cause dropouts or signal losses on areas of the tape. To provide the required force on the tape, these slack limiters must have resilient portions. As the materials used for cassette housings do not exhibit the requisite properties, the slack limiters must be formed from materials other than the material of the cassette housing itself. Thus, the pressure-applying slack limiter cannot be molded directly into the cassette housing and must be attached as a separate part after forming the housing. One attachment method involves engaging a notch of the slack limiter with a projection on the housing. Other methods involve a housing receptacle receiving and holding a mounting portion of the slack limiter, or simply holding the slack limiter by adhesive or friction.
These slack limiters have numerous cost and manufacturing disadvantages. The slack limiters cost $3.00 to $5.00 per thousand. In cassettes where a savings of tenths of one cent per cassette is significant, this material cost is large. Also, assembling the slack limiters in the cassette adds a manufacturing cost. The slack limiters are typically placed in the cassette from large rolls from which the slack limiters are cut. The rolls must be discarded or recycled. The winds of the slack limiters on the roll are separated by a liner layer which must be discarded, thereby adding waste. Moreover, to the extent the cassettes are recycled after their useful life, the slack limiter adds an additional component of a different material from the rest of the cassette which must be sorted out, thereby increasing recycling costs. Additionally, when the roll is empty, the production line on which the cassettes are made must be shut down to permit replacement of the roll. This down time further increases manufacturing costs.